Immune colloidal gold technology uses colloidal gold as a tracer marker or chromogenic agent, and is a labeled immunoassay technology applied to antigen-antibody reaction. The technology mainly includes two types of colloidal gold immunohistochemical technology and colloidal gold immunoassay technology. The immunocolloidal gold technology mostly uses nitrocellulose (NC) membrane as the solid phase carrier. The two commonly used rapid test methods are dot immunogold filtration assay (DIGFA) and dot immunogold chromatographic assay (DICA). Spot gold immunodiafiltration test is a detection method that combines colloidal gold labeling technology and immunodiafiltration technology with solid-phase carrier, and uses the aggregation and coloration of colloidal gold-labeled complex on the solid-phase membrane to judge the result.

Dot immunogold chromatographic assay is a solid-phase membrane immunoassay technology that combines colloidal gold labeling technology and protein chromatography technology with NC membrane as the carrier.

Colloidal gold immunoassay has the following advantages:

① The amount of reagents and samples is small, and the sample volume can be as low as 1-2 μl;

② It does not require special equipment such as gamma counters, fluorescence microscopes, enzyme label detectors, and is more suitable for on-site applications;

③ There is no pollution of harmful substances, such as radionuclides, phenylenediamine, etc.;

④The experimental results can be stored for a long time;

⑤The time is greatly shortened and the detection speed is improved. Various tests based on immunochromatography and immunodiafiltration are easy and fast to operate. At the same time, operators do not need to undergo strict technical training, and the reagents are stable, which especially meets the requirements of "bedside testing".